fix(network-activity-plugin): isolate react-native-nitro-fetch into separate bundle chunk

[V3RON]

Problem

Metro has a known issue (facebook/metro#836) where optional require() calls fail to resolve correctly even when wrapped in try/catch. This caused react-native-nitro-fetch — an optional dependency — to break bundling in some Metro configurations.

Solution

Follows the same pattern already in place for react-native-sse / event-source.ts:

• Extract the require('react-native-nitro-fetch') call from nitro-network-inspector.ts into a dedicated get-nitro-module.ts file.
• Add get-nitro-module.ts to Vite's manualChunks so Rollup emits it as a separate bundle chunk.

Metro loads each chunk independently, which sidesteps the optional-dependency resolution bug.

Changes

• src/react-native/nitro-fetch/get-nitro-module.ts — new file with the isolated getNitroModule getter
• nitro-network-inspector.ts — removes loadNitroModule, imports from the new file; exports NitroModule type
• vite.config.ts — adds get-nitro-module.ts to manualChunks
• .changeset/nitro-fetch-optional-dep-chunk.md — patch changeset